Drawing apparatus

ABSTRACT

Perspective effects in the basic lines of a technical drawing are obtained either by means of a transparent sheet marked with lines and placed on a drawing board illuminated from behind, or by use of a drawing board provided with a pivotable rule mounted on an arm that can be moved in a vertical direction, control means being provided so that the rule will alter direction and be aligned with one &#39;&#39;&#39;&#39;vanishing point&#39;&#39;&#39;&#39; over the whole vertical traverse of the supporting arm.

United St ates Patent 91 Sartori Jan. 8, 1974' [5 DRAWING APPARATUS 2,419,725 4/1947 Nosser 33/77 2,487,690 11/1949 Black et al 33]] K [76] Invent f Sam", resldfince Jeanne 3,457,648 7/1969 Baudat et al 33/77v gArc, we Jeanne d Arc, 3,456,352 7/1969 Bowen 33/76 rance FOREIGN PATENTS OR APPLICATIONS [22] Med: 3 1971 411,816 1/1945 ltaly 33/77 211 App] 10 0 283,461 10/1952 Switzerland 33/80 820,722 9/1959 Great Bntaln 33/77 [30] Foreign Application Priority Data Primary Examiner Han.y Hamian Jan. 14, 1970 France 7001484 Att n y-Waters, Roditi, Schwartz & Nissen Dec. 22, 1970- France 7046928 57 ABSTRACT [52] US. Cl. 33/77 1 51 1m. 01 B43l 13/14 Perspecuve effects baslc Emma 58 Field of Search 33/1 K, 77, 76, so; drawing are P by means transmit 108/23 sheet marked w1th lmes and placed on a drawmg 7 board illuminated from behind, or by use of a drawing [561 CM 2217192121:1:1;12127212312212:1:12;:

UNITED STATES PATENTS means being provided so that the rule will alter direc- 155726 10/1874 9 33/77 tion and be aligned with one vanishing point over lii 1 1x3 1: I l n the whole vertical traverse of the supporting arm.

222,271 12/1879 Hamilton 33/77 19 Claims, 21 Drawing Figures PATENTEDJAN 8 1914 SHEU 1 [IF 4 PATENTED JAN 8 SHEET 3 BF 4 'PATENTEBJAN 8191 4 SHEET u BF 4 DRAWING APPARATUS This invention relates to a method for graphic representation and also to drawing equipment for facilitating and rendering more rapid the production of perspective views of the Various elements, members or assemblies of a structure.

According to one aspect of the present invention, there is provided a method and equipment for drawing perspective views, wherein there is used a basic matrix squaring or cross-lining, to afford axial lines and vanishing lines having a predetermined angle in all the field depths, the trace or ground plan being disposed on a translucent panel of a support-table that is adapted to be illuminated from behind, so that said trace or ground plan will appear through a sheet of paper disposed on said panel.

According to another feature of the present invention, there is provided a method and apparatus for drawing perspective views, wherein the apparatus comprises a vertically adjustable support table having a fixed hollow portion fast with a leg to constitute a magazine for sheets of paper, and a pivotable lid comprising two spaced, transparent or translucent plates between which is introduced a standardised format means or a basic matrixoutline, there also being provided a pivotable, opaque panel that occupies, in one position, the rear of the pivotable lid below lighting means located rearwardly of the plates or, in another position, the projection of rays of light ontosaid plates during employment of a projector secured to the rear portion of the fixed hollow portion, the apparatus also comprising balance means so that the lid may be raised with little effort and also a strut for the maintenance of the lid in the inclined working position, the lid also comprising a recessed portion of greater depth than the rest of the lid located in one of the vertical sides of the lid for receiving a mechanism controlling an arm of a drafting apparatus.

According to a further aspect of the present invention, there is provided drawing apparatus comprising a board and a rule pivotably supported by an arm running on at least one rail located at the edge of said board, the rule being pivotable by means of a connecting rod pivotably secured at its opposite end to a pitman whose other end is guided by a rail whose angular position relative to the above mentioned support arm guide means may be varied, such that on displacement of the support arm along said guide with the rail in an inclined position the pitma'n will be displaced relative the support arm, and the rule will pivot such that lines drawn along its edge will all meet at one point.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be directed, by way of example, to the accompanying drawings, in which:-

FIG. 1 is a plan view 'of a squared or cross-linked basic ground plan according to the invention,

FIG. 2 is a diagrammatic view of drawing apparatus according to the invention,

FIG. 3 is a side view of drawing apparatus according to the invention,

FIG. 4 is a rear perspective view of a supportable according to the invention,

FIG. 5 is a front perspective view, to a larger scale, of the support table shown in FIG. 4,

FIG. 6 is a plan view of the apparatus as shown in FIG. 5, with the mechanical details revealed,

FIGS. 7 to 10 are plan views similar to that of FIG. 6, but showing different positions thereof,

FIG. 11 is a detailed plan view of part of the apparatus shown in FIG. 6,

FIG. 12 is a side view, partly in section, of a sliding bearing for use in the apparatus of FIG. 6,

FIG. 13 is a plan view, to a larger scale, of parts shown in FIG. 11,

FIG. 14 is a detail view of an alternative mechanism to that shown in FIG. 13,

FIG. 15 is a plan view of a drafting rule according to the invention, FIG. 16 is a side sectional view along line 8-8 of FIG. 15,

FIG. 17 is a side sectional FIG. 15,

view along line c c of FIG. 18 is a plan view illustrating, by way of example,

It is well known that if an object is viewed from an angle, the apparent shape of the object is deformed. Thus, it is' well known that a circle becomes in perspective an ellipse. Reduction of these deformed views to paper necessitates lengthy and complex drawing operations, and it is an object of the invention to provide a novel method and appropriate means for the rapid production of the essential lines of such views, particularly in perspective. I

According to this method, there is used a basic matrix ground plan (refer to FIG. 1) taking the form of a squared or cross-lined frame work prepared over all or only a portion of a support 1. This support may consist directly of the sheet of paper onto which the perspective drawing is to be drawn and, in this case, the cross-lining is effected with an ink or special product which is not visible on making reproductions of the drawing. Preferably, however, such cross-ruling is drawn on an independent and translucent sheet in such a manner that it will readily appear through the drawing sheet under the influence of illumination supplied behind the support 1. The support 1 has a format such that it will correspond to the standard formats and the cross-lining comprises a plurality of lines or traces, consisting of right-angle cross-lining comprising vertical lines la which afford the vertical axis and horizontal lines 1b constituting the interlining guides which also permit the regular and uniform distribution of the datum or reference indications of the objects drafts. Furthermore, there is provided on the said support 1 angular cross-ruling obtained by intersection of inclined lines 10 and 1d, which lines afford the so-called vanishing lines. The said inclined lines It: and 1d are disposed to be symmetrical or nonsymmetrical relative to the vertical reference axis and they afford the advantage that they permit the utilisation of an ellipse having the same characteristic throughout the depth of the vanishing lines employed, without in this way bringing about visual distortion of the drawing. It will also be noted that the median vertical axis is graduated in mil limetres so as to define'the vertical positions.

It should be appreciated that, according to a feature of the invention, the judicious determination of the angle of inclination of the vanishing lines 1c and 1d as a function of the vertical or horizontal angle of inclination employed in the drafting accessories, such as means for drawing ellipses, permits the uniform use of the same type of such means with respect to all depths of the draughting field.

Thus, by way of non-limitative example and referring to cases wherein a means for drawing ellipses is used, or one having a vertical angle of about or a horizontal angle of about 30, the lines 1c and 1d determining an average vanishing line could have, relative to the horizontal, an angle of inclination of approximately 10.

However, as already emphasised, said mean vanishing line angle could vary and is determined as a function of the accessories utilised.

In complementary fashion, and with a view to facilitating the location of possible correctives, the vertical lines la are numbered starting from the vertical axis of the cross-lining, whereas the vanishing lines are also numbered with this end in view. According to a further provision, there is incorporated in said basic crosslining a reducing scale permitting the immediate interpretation of the natural dimensions of the object to be represented, so as to convert them to those corresponding to the scale involved in the graphic representation. Provision is also made for the application of a corrective factor for the so-called horizontal sides and availing itself of the vanishing lines.

The basic matrix cross-lining having been prepared on a translucent support, it will readily be appreciated that when it is disposed on the top of a drawing board equipped with illuminating means disposed behind the top thereof, said cross-lining is clearly visible through the sheet of paper disposed over the cross-lining.

In this particularly simplified embodiment of the invention, the method of producing the drawing consists in utilising the rule and ellipse-tracing means, these elements being oriented in accordance with the lines and traces of the basic matric cross-ruling.

There will now be described an exemplary embodiment of the invention which does not require the basic cross-lining already described, but allows the mechanical production of perspective views in a direct manner.

Referring to FIG. 2, a drawing apparatus as described above is fitted with a part-2 which has fast therewith a handle 3 in order to permit the manual displacement thereof in the vertical or horizontal direction, a balancing system being provided for facilitating the displacement, an assembly of telescopic type permitting the apparatus to cover the entire surface of the table. The apparatus may have secured to it various accessories, notably ellipse drafting means.

The apparatus according to the invention also comprises an angle selector shown diagrammatically at 4 permitting orientation of said apparatus through the intermediary of an angle-reading lever 5 pivoted about a pivot 6 and at the same time obtaining its movements from a slideway 7 which is itself oriented by means of an assembly articulated at 8.

The apparatus being thus designed, it will readily be appreciated that it becomes possible therewith to oriented the accessories which it supports, depending upon the angle employed for the drawing of the perspective view. In proportion as the displacement thereof proceeds in all directions, the selector 4 permits the automatic effecting of a correction in respect of the inclination of the ellipse drafting means relative to the angle of inclination imparted to the lever 5, in such a manner as to preserve, in respect of the accessory mounted on the handle, a mean angle of inclination relative to the vanishing lines 10 and 1d thus defined. Locking means are also provided in such a manner as to make it possible to lock the apparatus in a predetermined position which will be useful for the preparation of the drawing. Thus, the apparatus may be used as a simple vertical or horizontal rule.

A further embodiment is illustrated in FIGS. 3 to 5. A support table 11, which is designed in the form of a suitcase having a vertically adjustable lockable leg, comprises a lower fixed and hollow portion 11 for receiving sheets or drawings. A pivotable lid 11 is fixed in an open position by a double strut member 12 having a longitudinal cross-piece 12 A force-compensating means 13 interposed between said lid 11 and the base portion 11 1 facilitates the raising thereof whilst providing a retarding force as the lid 11 is let down into the closed position.

The working face of the pivotable lid 11 is constituted by two transparent or translucent plates 14 and 15 spaced apart to receive either a standard format means F or the sheet 1 comprising the basic matrix trace as described earlier. However, a single transparent plate may be employed, there having been printed or otherwise marked on that plate the format or other useful indication means. Parts 11, 11 11' as well as 14 and/or 15 constitute a drafting board.

The lid 11 is provided with a cavity to the rear of the plates 14 and 15, in which is lodged a source of electric illumination 16 which illuminates the drawing from the rear, an opaque, pivotable panel 17 blocking said cavity and constituting the end face thereof.

The panel 17 may hinge downwardly and bear on the longitudinal cross-piece l2 (see FIG. 4). In this position, after having extinguished the illuminating means 16, it is possible to mount a projector P to the rear of the base portion l1 (see FIG. 3), to project films or photographs at an appropriate location on the plates 14 and 15, which the user then may trace off on the working face. According to a further provision, there is lodged within or externally of the pivoting lid 11' a roll of drawing paper 18 which issues to the front through an appropriate slot, a paper cutter incorporated in said lid permitting the cutting thereof to the desired length. In the same manner, it is possible to provide a guard shutter 19 mounted on a spring drum to cover the drawing when the latter is not being worked on.

The pivotable lid 11 has formed therein, along one of its vertical sides, a recessed portion 11 of greater length than the rest of the lid, wherein is lodged the mechanism of the drafting apparatus, whereas the opposite side thereof constitutes a magazine 11 for containing the tools of the draftsman.

The drawing apparatus according to this embodiment comprises a horizontal arm 20 which slides along a vertical guide 25 located in the recessed portion 11. As shown in FIG. 12, the arm 20 slides over rollers 21, 22, 23 and 24 on the opposite sides of the vertical guide 25. The opposite rollers 21 and 24, which are diagonally arranged, support the descending load of the arm 20, whereas the rollers 22 and 23 are mounted with a small clearance, so that they are in this way stressed only during the raising of said arm.

According to a further provision, the rollers 21 and 24 are mounted on eccentric pivots with a view to regulating the horizontal location of the arm and consequently of a drafting rule 30 to be described hereinafter.

Referring to FIG. 6 and 13, the arm 20 has a pitman B slidably located therein. The pitman B is pivoted to a crank or connecting rod 27 at the free end of the arm 20, the crank 27 being pivoted about a pivot 28. A graduated disc 29 fast with the drafting rule 30 also pivots about the pivot 28. The freely rotatable disc 29 and drafting rule 30 can be locked to the crank 27 by a retractable pin 31 co-operating with a notch 29 in the example illustrated in the drawing.

The other end of the pitman B is provided with a pair or rollers 32 arranged on either side of a rail 33, which extends through slots in the arm 20. The rail 33 is connected by a pivot 34 to the vertical guide and is consequently able to occupy a number of angular positions relative to the guide 25, as illustrated in the FIG. 6. For this purpose, the lower portion of the vertical guide 25 has secured thereto a removable and interchangeable plate 35 formed with notches 35, 35 and 35 arranged symmetrically with respect to the axis of the vertical guide 25.

A locking or retaining means 36 disposed at the end of the rail 33 co-operates with one of the notches 35, 35 or 35 to secure the rail in some particular angular position with respect to the guide 25.

The plate 35 could be replaced by a rotatable drum having, on each of its faces, any desired distribution of the notches for positioning the rail 33.

The above arrangement operates as follows. The drafting rule is locked to the crank 27, as previously described, in the desired angular position. The rail 33 is then locked in a particular angular position, for ex? ample that shown in FIG. 6. This is done with the rule 30 occupying a horizontal position and at that position on the sheet of paper at which it is desired to place the horizon. This position is shown in FIG. 6. If the arm 20 is moved upwardly, the pitman B is moved to the left, as seen inFlG. 6, as the rail 33 moves towards the guide 25. The crank 27 is therefore moved clockwise and the rule 30 is tilted further as vertical displacement increases. In fact, over the traverse of the arm 20 lines drawn on the straight edge of the rule 30 will all converge to one point. It will be obvious that this forms a very convenient method of drawing vanishing lines on v a piece of paper, particularly if the vanishing point is off the sheet.

In the case where the rail 33 is locked in the left-hand notch (as illustrated in FIG. 7) it will be noted that the vertical displacement of the horizontal arm 20 on the vertical guide 25 causes the rotation of the drafting rule 30 in an anti-clockwise direction. The vanishing point of the lines y-x and y'-x' will be to the left of the drafting rule rather than to the right as in FIG. 6.

The drafting rule 30 can occupy various angular positions relative to the crank 27 (see also FIG. 11). The pin 31 engages the notch 29', the graduated disc 29 being rotatable when this pin 31 is retracted, so that a graduation may be compared with a fixed index I of disc 29, so that a desired angle may be set. After this adjustment, a locking means such as a nut and screw 39 provides for locking of the disc 29 to the crank 27. This feature permits verticalv adjustment of the vanishing point.

With reference to FIG. 9, it will be observed that for the same positions of the horizontal arm 20 and of the rail 33 as are shown in FIG. 7, the vanishing points are displaced over a symmetrical distance by rotation of the rule 30 over It will be noted that, if the rail is placed parallel to the guide 25, the inclination of the rule 30 is constant during vertical displacement of the horizontal arm 20, thus allowing the production of sloping and parallel lines, as in a conventional drawing board.

Referring to FIGS. 8 and 10, these correspond to FIGS. 7 and 9, except that the rail 33 is angularly locked to the right-hand notch 35. In this case, the vanishing points are situated to the right of the rule 30.

These features in respect of the formation of converging lines obtained by the drafting apparatus permit the judicious drafting of the vanishing lines of any isometric, trimetric or dimetrie perspective view, as illustrated in FIG. 18.

According to a further provision of the invention, the length of the crank 27 may be varied by rendering adjustable a value D of the length between the pivot 28 of the crank 27 and the pivot 26 for the coupling of the pitman B (see FIG. 13). The value D may be varied by means of, for example, a nut and screw system. This adjustment varies the horizontal position of the two vanishing points. However, this may also be done by swinging the rail 33 to a greater angular position from the guide 25. r

Due to the circular movement of the pivot 26 of the pitman B the lines drawn on the rule 30 are not quite all convergent. This may be corrected by means of the arrangement shown in FIG. 14, where the end of the pitman B is formed in a rack 37, and the crank 27 is replaced by a gear 27. having a symmetrically corrected profile, so that all the above-mentioned lines are acurately convergent. A leaf spring is provided to keep the rack 37 constantly in mesh with the gear 27 In the same manner, according to a further provision there is provided a plurality of positions of the pivot 34 on the vertical guide 25 solely for the purpose of modifying the inclination of the rail 33 relative to the axis of the guide 25.

Referring to FIG. 11, the graduated disc 29 that is fast with the rule 30 is moved by means of a knob 38 that is formed on its periphery with notches. The knob 38 permits the movements of the arm 20 and of the graduated disc 29 whereas the rotation thereof produces the automatic disengagement of the locking means 36 for the notches 35, 3S and 35 for the angular displacement of the rail 33. To this end, it should be noted that a handle may also be secured on the pitman B for providing such control.

A locking means 40 fast with the arm 20 (see FIG. 11) is designed toact perpendicularly on one of the support faces of the guide 25 so as to permit the locking of the apparatus in any desired position.

A counterweight 41 balances the entire mass of the drafting apparatus and facilitates the handling thereof. The counterweight 41 is supported by a cable 42 secured at its ends to the upper and lower parts of the end of the arm 20 and is guided by pulleys 43 and 44. The cable 42 is kept under tension by a coil spring 45.

The arm- 20 is provided with a spring-loaded pin 46 that is retractable by means of a lever 47 and cooperates with a series of notches 48 formed at regular intervals in the side of a strip or scale 48 that is secured parallel to the vertical guide 25. This pin 46 holds the arm 20 in a series of regularly spaced vertical positions, and thus automatically permits the uniform positioning of the arm 20 for drawing, shading or hatching, for example as illustrated in FIG. 6.

Referring to FIG. 11 it should also be noted that, when the drafting rule 30 is freely pivotable due to the unlocking of the retractable pin 31 and the nut 39, so that the draftman may produce lines of variable directions, the horizontal position may be found automatically by means of a spring-loaded lever 49 that engages in a notch formed in the knob 38. This arrangement means that the user does not have to use the pin 31 or the nut 39 every time.

The drafting rule 30 is also angularly adjustable relative to the horizontal by means of an intermediate plate 50 which is secured to the graduated disc 29.

Referring now to FIGS. to 21, the rule 30 is formed with a recess 30. A removable scale 51 is mounted above that edge with a small gap between the rule and the scale. The scale 51 may be graduated either in millimetres or to a logarithmic or other scale. A slide 52 is provided with a flange that extends into the gap between the scale 51 and the rule 30 so that it is slidable along the scale 51 A pivotable and retractable stop 54 is mounted on the said slide and, when in the position shown in full lines in FIG. 17, affords a positioning abutment for the drafting matrices. A knurled adjusting screw 53 clamps scale 51 against the flange of slide 52, as shown.

The recess 30 of the rule 30 is designed to be engaged by a complementary flange 55 of the longitudinal sides of drafting matrices 55 (see FIG. 16) in such a manner as to permit the accurate positioning thereof and to afford a guide during sliding movement. Furthermore, if the'rule 30 is removed from the working surface, this arrangement, with the scale 51, prevents the matrices or stencils 55 from sliding down the back of the rule 30, or from falling down the front thereof when the rule is in its working position.

In the case of matrices or stencils 56 which are intended in particular for the drafting of elipses and adapted to be fitted on the rule 30, the stencil illustrated in FIG. 19 has an axis of symmetry 56 allowing accurate axial and longitudinal positioning. The axis 56 is provided with openings 56 of a rhombic shape that allow a pencil to be inserted therethrough and reference marks to be made on the sheet, this being followed by drafting for the production of successive ellipses by causing the matrix to slide.

Each stencil 56 may be used perpendicularly in abutment on the rule 30, as shown in FIG. 19. For this purpose, the transverse sides are formed with bulges 56 constituting end abutment points which thus ensure satisfactory positioning.

It should also be noted that the matrices or stencils 56 are provided, along their longitudinal edges, with graduations 56 and 56 Scale 56 is in millimetres whereas the scale 56 is a logarithmic scale.

Each stencil or matrix 56 comprises a plurality. of ellipses arranged coaxially, the nominal dimensions of which are determined, for example, as a function of the standard dimensions of the inner and outer diameters of ball bearings. Each ellipse 57 is further located by means of its major diameter 57, the axis of symmetry 56 and also by radii 57 at 45 to the axes.

This arrangement is useful in the case of sections through cylindrical parts, shown in perspective.

In the case of matrices 58 used as letter stencils (FIG. 20), the same tuming features are again encountered having, a distance A measured from their hearing edges to the basis of the characters, the values A being constant and related to the size of parallel lining afforded by the notches 48 in the scale 48.

The stencils 58 are also provided with apertures for, where necessary, underlining the written text.

A matrix 59 shown in FIG. 21 has the same positioning features, but the upper row of numerals or letters is inverted so that they are brought into use by pivoting the stencil about the long axis, whereas the example shown in FIG. 20 is turned through in its own plane.

I claim:

1. An apparatus for drawing perspective views, comprising: a table having a lower hollow housing supported on adjustable leg means; a lid pivotally attached along a forward edgeof said housing; said lid having spaced, translucent plates at the forward side thereof, between which a translucent panel is adapted to be placed, and an opaque panel pivotally mounted at the rear side of said lid; said translucent panel having a basic matrix cross-lining thereon to afford axial lines and vanishing lines having a predetermined angle in all field depths; said lid havinglighting means thereon between said plates and said opaque panel; the latter being pivotal to occupy one position to close off the rear portion of said lid, to be lowered to another position adjacent said housing to expose the rear of said plates, to allow the projection of images from a projector mountable on said housing; strut means for supporting said lid in an inclined working position; and force compensating means interposed between said lid and said housing for facilitating the raising of said lid and providing a retarding force as said lid is closed; the latter further having an elongated recessed portion extending outwardly from one of the vertical sides thereof, and a mechanism for controlling support of a drafting device slidably mounted in said recessed portion.

2. The drawing apparatus as defined in claim 1, wherein said lid further includes, behind said translucent plates, a roll of paper the web of which extends through a slot; and further comprising paper cutting means incorporated in saidlid, the paper tobe fed onto the working surface of an outennost plate past said paper cutting means; said lid also including a shutter mounted on a spring drum, to cover the working sur.- face.

3. The drawing apparatus as defined in claim 1, wherein said strut means includes a double crutch pivoted on said hollow housing, including a cross-piece on which rests said opaque panel, upon disengagement thereof from said rear portion of the lid.

4. The drawing apparatus as defined in claim 1, further comprising a support arm slidable above said translucent panel; and wherein balancing means is mounted on said lid, formed by a counterweight connected to the ends of a cable which is tensioned by a spring and guided by pulleys; said cable being secured to each side of said support arm.

5. The drawing apparatus as defined in claim 4, wherein said lid further includes a scale secured substantially perpendicular to said support arm and having notches therein; and a spring-loaded pin extending from said support arm, cooperating with said notches in the scale in order to provide spaces stopped positions of said support arm.

6. An apparatus for drawing perspective views, comprising in combination: a support table having a translucent panel thereon adapted to be illuminated from behind and constituting a drafting board, said panel having a basic matrix cross-lining thereon to afford axial lines and vanishing lines, and said lining appearing through a sheet of paper disposed on said panel; a vertical first guide rail fixably secured to one edge of said table; an angularly adjustable second guide rail pivotally secured to one end of said first rail; adjusting means on the other end of said first rail for adjusting the angular position of said second rail relative to said first rail; a support arm extending over said panel, slidably mounted on said first rail; a pitman slidably mounted on said support arm for movement in a direction perpendicular to said first r'ail; said pitman having one end slidably mounted on said second rail, and its other end pivotally connected to a connecting rod, the latter being pivotally mounted on said support arm; and a drafting rule adjustably secured to said connecting rod; wherein, when said support arm is displaced over said panel along said first rail, said pitman slides later ally thereof due to the angular orientation of said second rail, and pivots said connecting rod and said drafting rule such that lines drawn along said rule, in all vertical positions of said support arm, will meet at substantially one vanishing point.

7. The drawing apparatus as defined in claim 6, wherein said connecting rod is coupled by a springbiased, retractable pin to a pivotable, graduated disc having an index and a knob mounted thereon and being secured to said'drafting'rule; said knob having means mounted thereon to establish horizontal positioning of said rule when said second guide rail is disposed parallel to the axis of said first guide rail; said retractable pin permitting, when disengaged, free axial rotation of said disc relative to said index for angular orientation of said rule; and means for locking said disc in any angular position.

8. The drawing apparatus as defined in claim 7, further comprising a resilient lever engageable in said knob and carrying a pin; said knob being notched in its periphery for cooperation with said pin, for effecting said horizontal positioning of the rule after free rota tion thereof.

9. The drawing apparatus as defined in claim 7, further comprising an intermediate plate fast with said disc, so that said rule is angularly adjustable relative to the horizontal by means of said intermediate plate.

10. The drawing apparatus as defined in claim 6, wherein the edge of said rule is provided with a recess permitting the engagement of drafting stencils having complementary profiles for the purpose of preventing the disengagement thereof, said edge of the rule also being provided with a detachable graduated stripv mounted at a small distance therefrom, and a member slidably and lockably mounted on said strip, said memher having a retractable stop mounted thereon for engaging said stencil.

11. The drawing apparatus as defined in claim 10, further comprising matrices for drawing ellipses of standardized dimensions, said matrices having a longitudinal symmetry axis permitting them to be turned over, centering apertures on said symmetry axis permitting the adjustment thereof by reference marks, said matrices being formed along their transverse edges with bulges constituting points for abutment on said rule when they are used in a perpendicular position, there also being provided at least one graduation on at least one longitudinal edge of said matrices.

12. The drawing apparatus as defined in claim 6, wherein said adjusting means includes a plate secured to said first guide rail and including several positioning notches for the engagement and centering of mating, manually operable retaining means secured to the end of said second guide rail, and wherein the latter is locked at its free end by said plate.

13. The drawing apparatus as defined in claim 12, further comprising a handle on said rule, and wherein said retaining means includescontrol means acting by rotation exerted on said handle.

14. The drawing apparatus as defined in claim 6, further comprising means for balancing the apparatus during the displacement thereof.

15. The drawing apparatus as defined in claim 6, wherein the angular orientation of said rule relative to said connecting rod permits the drawing of parallel lines when said at least one rail is disposed parallel to the axis of said vertical guide, and of lines converging substantially to a point when the same rail is disposed obliquely to said guide.

16. The drawing apparatus as defined in claim 6, wherein the coupling point between said pitman and said connecting rod is adjustable with respect to the pivot of the latter, for adjusting the angular amplitude of the movement of said rule during vertical displacement of said support arm.

17. The drawing apparatus as defined in claim 6;

wherein one end of said pitman is formed as a rack and said connecting rod has thereon a pinion engaging said rack, the profile of said pinion being such as to correct movement of said rule so that lines drawn on the edge thereof converge to one point.

18. The drawing apparatus as defined in claim 6, further comprising braking means secured to said support arm, which acts on said vertical guide to permit locking of the apparatus at a desired height.

19. The drawing apparatus as defined in claim 6, wherein said support arm is formed with a springloaded pin co-operating with notches formed at regular intervals in a fixed scale, for allowing vertically controlled displacement of said arm, and providing spaced stopped positions of said support arm for the drawing of interlining and shading. 

1. An apparatus for drawing perspective views, comprising: a table having a lower hollow housing supported on adjustable leg means; a lid pivotally attached along a forward edge of said housing; said lid having spaced, translucent plates at the forward side thereof, between which a translucent panel is adapted to be placed, and an opaque panel pivotally mounted at the rear side of said lid; said translucent panel having a basic matrix cross-lining thereon to afford axial lines and vanishing lines having a predetermined angle in all field depths; said lid having lighting means thereon between said plates and said opaque panel; the latter being pivotal to occupy one position to close off the rear portion of said lid, to be lowered to another position adjacent said housing to expose the rear of said plates, to allow the projection of images from a projector mountable on said housing; strut means for supporting said lid in an inclined working position; and force compensating means interposed between said lid and said housing for facilitating the raising of said lid and providing a retarding force as said lid is closed; the latter further having an elongated recessed portion extending outwardly from one of the vertical sides thereof, and a mechanism for controlling support of a drafting device slidably mounted in said recessed portion.
 2. The drawing apparatus as defined in claim 1, wherein said lid further includes, behind said translucent plates, a roll of paper the web of which extends through a slot; aNd further comprising paper cutting means incorporated in said lid, the paper to be fed onto the working surface of an outermost plate past said paper cutting means; said lid also including a shutter mounted on a spring drum, to cover the working surface.
 3. The drawing apparatus as defined in claim 1, wherein said strut means includes a double crutch pivoted on said hollow housing, including a cross-piece on which rests said opaque panel, upon disengagement thereof from said rear portion of the lid.
 4. The drawing apparatus as defined in claim 1, further comprising a support arm slidable above said translucent panel; and wherein balancing means is mounted on said lid, formed by a counterweight connected to the ends of a cable which is tensioned by a spring and guided by pulleys; said cable being secured to each side of said support arm.
 5. The drawing apparatus as defined in claim 4, wherein said lid further includes a scale secured substantially perpendicular to said support arm and having notches therein; and a spring-loaded pin extending from said support arm, cooperating with said notches in the scale in order to provide spaces stopped positions of said support arm.
 6. An apparatus for drawing perspective views, comprising in combination: a support table having a translucent panel thereon adapted to be illuminated from behind and constituting a drafting board, said panel having a basic matrix cross-lining thereon to afford axial lines and vanishing lines, and said lining appearing through a sheet of paper disposed on said panel; a vertical first guide rail fixably secured to one edge of said table; an angularly adjustable second guide rail pivotally secured to one end of said first rail; adjusting means on the other end of said first rail for adjusting the angular position of said second rail relative to said first rail; a support arm extending over said panel, slidably mounted on said first rail; a pitman slidably mounted on said support arm for movement in a direction perpendicular to said first rail; said pitman having one end slidably mounted on said second rail, and its other end pivotally connected to a connecting rod, the latter being pivotally mounted on said support arm; and a drafting rule adjustably secured to said connecting rod; wherein, when said support arm is displaced over said panel along said first rail, said pitman slides laterally thereof due to the angular orientation of said second rail, and pivots said connecting rod and said drafting rule such that lines drawn along said rule, in all vertical positions of said support arm, will meet at substantially one vanishing point.
 7. The drawing apparatus as defined in claim 6, wherein said connecting rod is coupled by a spring-biased, retractable pin to a pivotable, graduated disc having an index and a knob mounted thereon and being secured to said drafting rule; said knob having means mounted thereon to establish horizontal positioning of said rule when said second guide rail is disposed parallel to the axis of said first guide rail; said retractable pin permitting, when disengaged, free axial rotation of said disc relative to said index for angular orientation of said rule; and means for locking said disc in any angular position.
 8. The drawing apparatus as defined in claim 7, further comprising a resilient lever engageable in said knob and carrying a pin; said knob being notched in its periphery for cooperation with said pin, for effecting said horizontal positioning of the rule after free rotation thereof.
 9. The drawing apparatus as defined in claim 7, further comprising an intermediate plate fast with said disc, so that said rule is angularly adjustable relative to the horizontal by means of said intermediate plate.
 10. The drawing apparatus as defined in claim 6, wherein the edge of said rule is provided with a recess permitting the engagement of drafting stencils having complementary profiles for the purpose of preventing the disengagement thereof, said edge of the rule also being provided with a detachable graduated strip mounted at a small distance therefrom, and a member slidably and lockably mounted on said strip, said member having a retractable stop mounted thereon for engaging said stencil.
 11. The drawing apparatus as defined in claim 10, further comprising matrices for drawing ellipses of standardized dimensions, said matrices having a longitudinal symmetry axis permitting them to be turned over, centering apertures on said symmetry axis permitting the adjustment thereof by reference marks, said matrices being formed along their transverse edges with bulges constituting points for abutment on said rule when they are used in a perpendicular position, there also being provided at least one graduation on at least one longitudinal edge of said matrices.
 12. The drawing apparatus as defined in claim 6, wherein said adjusting means includes a plate secured to said first guide rail and including several positioning notches for the engagement and centering of mating, manually operable retaining means secured to the end of said second guide rail, and wherein the latter is locked at its free end by said plate.
 13. The drawing apparatus as defined in claim 12, further comprising a handle on said rule, and wherein said retaining means includes control means acting by rotation exerted on said handle.
 14. The drawing apparatus as defined in claim 6, further comprising means for balancing the apparatus during the displacement thereof.
 15. The drawing apparatus as defined in claim 6, wherein the angular orientation of said rule relative to said connecting rod permits the drawing of parallel lines when said at least one rail is disposed parallel to the axis of said vertical guide, and of lines converging substantially to a point when the same rail is disposed obliquely to said guide.
 16. The drawing apparatus as defined in claim 6, wherein the coupling point between said pitman and said connecting rod is adjustable with respect to the pivot of the latter, for adjusting the angular amplitude of the movement of said rule during vertical displacement of said support arm.
 17. The drawing apparatus as defined in claim 6; wherein one end of said pitman is formed as a rack and said connecting rod has thereon a pinion engaging said rack, the profile of said pinion being such as to correct movement of said rule so that lines drawn on the edge thereof converge to one point.
 18. The drawing apparatus as defined in claim 6, further comprising braking means secured to said support arm, which acts on said vertical guide to permit locking of the apparatus at a desired height.
 19. The drawing apparatus as defined in claim 6, wherein said support arm is formed with a spring-loaded pin co-operating with notches formed at regular intervals in a fixed scale, for allowing vertically controlled displacement of said arm, and providing spaced stopped positions of said support arm for the drawing of interlining and shading. 